Types: (1) Simple proportion (a:b = c:d) with product property a×d = b×c; (2) Continued proportion (a:b = b:c) where b is geometric mean; (3) Mean proportion/Geometric mean: b² = a×c; (4) Third proportion: If a:b = b:c, find c given a and b. Formula for third proportion: c = b²/a. Fourth proportion: If a:b = c:d, find d. Formula: d = (b×c)/a. Solving MCQs: Identify proportion type from wording. For mean proportion, solve b = √(a×c). For continued proportion, use b² = a×c. Exam tip: Mean proportion problems frequently appear. Practice calculating geometric means quickly.